Batteries on mobile devices drained more quickly by apps which are free, researchers say

Free apps are all well and good when you’re looking to save a few bucks, but new research suggests they might have you reaching for the battery charger more often than you would if you were using paid apps. And then there’s the long-term implications regarding battery life to consider too. The culprit? Why, those pesky ads, of course.

Researchers from Microsoft and Purdue University used a special energy profiling tool to find out more about how apps on Android and Windows Mobile phones affect battery life when run over a 3G connection. In one case in particular, 75 percent of an app’s power requirement was spent not on gameplay but instead on operating third-party ad services.

In its study, the research team used six popular smartphone apps — including Angry Birds and Facebook — and looked at how they performed on three HTC smartphones: the Android-powered Magic and Passion handsets, and a TyTN II running Windows Mobile. Apple’s iPhone wasn’t able to be tested because of restrictions built into its iOS operating system.

Fans of Rovio’s bird-flinging game may be surprised to learn that, with the free versions, only 20 percent of the game’s energy consumption was linked to gameplay. Forty-five percent was used for finding out the player’s location so that targeted advertising could be served.

The researchers also discovered what they called a “3G tail,” where the battery’s energy continues to be sapped even after a particular action, such as the download of information, has completed. With Angry Birds, for example, they found that this so-called 3G tail accounted for more than 25 percent of the app’s total energy consumption.

But the batteries needn’t be placed under quite so much pressure, the researchers said. By restructuring the source code on some of the apps they used in the study, they were able to reduce their total energy consumption by between 20 and 65 percent.

Of course, it’s annoying when you’re away from a power source and you see your battery life diminishing fast, but worse than that, inefficient apps will also be decreasing the overall life of your device’s battery at a faster rate than necessary. Maybe the paid version is looking like a more attractive option after all…